locate
locate is a common Unix tool for quickly finding files by name. It offers speed improvements over the find tool by searching a pre-constructed database file, rather than the filesystem directly. The downside of this approach is that changes made since the construction of the database file cannot be detected by locate. This problem can be minimised by scheduled database updates.
Over time, alternative implementations have replaced each others, from slocate (secure locate) that only showed files accessible to the user, to mlocate (merging locate) that merges databases at each update, which offers a performance speedup since it can skip previously examined files to today's plocate (posting locate) is a locate based on posting lists, consuming the database ahead-of-time and making a much faster (and smaller) index out of it.
Installation
While the GNU findutils also include a locate implementation, Arch's findutils package does not.
Usage
Before locate(1)[dead link 2024-10-13] can be used, the database will need to be created, this is done with the updatedb(8) command, which (as the name suggests) updates the database.
plocate contains a plocate-updatedb.timer unit, which invokes a database update each day and is enabled upon installation. Start it manually if you want to use it before reboot. You can also manually run updatedb as root at any time.
To save time, updatedb can be (and by default is) configured to ignore certain filesystems and paths by editing /etc/updatedb.conf. updatedb.conf(5) describes the semantics of this file. It is worth noting that among the paths ignored in the default configuration (PRUNEPATHS) are /media and /mnt, so locate may not discover files on external devices.
Troubleshooting
Btrfs
The default configuration prevents Btrfs filesystems from being included in the results. To allow including btrfs mountpoints, change the configuration line in /etc/updatedb.conf for PRUNE_BIND_MOUNTS to:
PRUNE_BIND_MOUNTS = "no"
Note of course that this also means other bind mountpoints also will be included. If you need to exclude these mountpoints, the PRUNEPATHS setting in the same configuration file can be used.